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1. Field of the Invention
The present invention relates to decorative lighting fixtures and to reflectors and filters for lights.
2. General Background of the Invention
Colored lighting has been used for centuries to convey moods and create special theatrical effects. Most colored light has been created by passing light through either colored gels, dichroic filters, or oil membranes. In either case the resulting color of light has been dependent on the color of the filter, or substance the light passes through. Diffraction gratings have been used in small scale optical displays that use combinations of light sources and light manipulating devices, to produce a variety of pleasing color effects. Due to the difficulty in keeping the polychromatic (undiffracted) light from interfering from the monochromatic (diffracted) light, most applications, especially those utilized by the lighting industry, have been quite limited in scope.
An example of a decorative optical display apparatus that employs a diffraction grating is U.S. Pat. No. 6,011,650 to Parker; William P. (hereinafter xe2x80x9cthe 650 patentxe2x80x9d). Discloses a decorative optical display utilizing a reflective diffraction grating or a transmissive diffraction grating and a plurality of polychromatic light sources disposed around perimeter of the reflective diffraction grating or perimeter of the transmissive diffraction grating. The light sources are disposed so as to the illuminate the reflective or transmissive diffraction grating at an oblique angle, respectively. The oblique illumination of the reflective or transmissive diffraction grating prevents a viewer from seeing undiffracted light rays or emanating from the light sources, which can detract from the appeal of the optical display pattern. The reflective or transmissive diffraction grating may be flat or curved and may be supported by a support member. Further, the reflective or transmissive diffraction grating may have either a single or multiple axes. A shade is provided to cover the light sources to prevent undiffracted light rays from reaching the viewer, or to hide wires connecting the light sources. Also, the activation of the light sources is controlled via a control unit, and can be set to any one of a number of different temporal and spatial activation modes. The optical display is also adaptable for a variety of uses calling for an attractive display, such as a clock or a display sign.
An example of a lighting fixture or lamp that employs a diffraction grating is U.S. Pat. No. 4,716,506 to Shang; Hui C. (hereinafter xe2x80x9cthe 506 patentxe2x80x9d). The 506 patent discloses an iris-producing lamp device comprising one or more non-monochromatic light sources with its socket or sockets mounted on bracket. A paraboloid mirror may be disposed behind each lamp socket and a light source in the focus of the paraboloid mirror and the lamp shade is made of a grating-film iris-producing glass with a non-monochromatic light source in it. Thus the lamp shade can reflect not only its original color but also the other colors when the lamp is shut-off while transmitting a variety of colorful patterns and projecting them to objects around the lamp device when the lamp is on.
While the optical display of the 650 patent does describe a way to display colored light patterns consisting of diffracted light that are not overpowered by the undiffracted light from the light source, it has several major limitations if it is to be used as a source of decorative illumination. The major limitation is that the display is basically contained within a flat panel and is designed to be viewed from one side only. Most decorative lighting fixtures are meant to be viewed from many angles. The other limitation is that the diffracted light created by the device is too weak to be projected over any distance because the multiple axial nature of the device weakens the clarity and strength of the diffracted light. The single axial nature of the light tube intensifies the clarity and strength of the display to the point that it envelopes the surrounding space with projected, prismatic light, whereas the 650 patent is not meant to illuminate its surroundings, but is designed as a pure display.
The third limitation is that motion and change to the display is achieved with an electronic means, whereas with the light tube, the color effect changes with the position of the viewer.
While the 506 patent does disclose a lamp that creates color with a diffraction grating and is bright enough to illuminate the surrounding space, it also has some major drawbacks. The first is that it is not always desirable to view undiffracted light through the transmissive grating because the undiffracted light tends to overwhelm the diffracted light. The second is that the interference created by the undiffracted light makes the projection of clear diffracted light nearly nonexistent.
The following U.S. Patents (and all references mentioned therein) are incorporated herein by reference: U.S. Pat. Nos. 3,388,246; 4,799,764; 4,109,305; 4,256,405; 4,716,506; 4,837,667; 4,843,529; 4,882,661; 5,077,645; 5,089,946; 5,247,491; 5,347,431; 5,440,469; 5,455,754; 5,517,391; 5,644,565; 5,672,003; 5,791,775; 5,997,151; 6,011,650.
The present invention relates to decorative lighting and may have broader applications as used in signage, a decorative sculptural element, or for instrumentation and navigation systems. The Spectral Light Tube produces a rainbow colored light field that appears to emanate from the central hollow shaft inside of the tube when illuminated with a light-source directed through the center of the tube. The invention includes a diffraction grating that is curved into an approximately cylindrical or tubular structure and one or multiple light sources that direct light through the open axis of the tubular structure. The light sources illuminate the grating at an oblique angle so that diffracted (monochromatic light) is projected on an axis perpendicular to the surface of the diffraction grating. Since the diffracted light is projected roughly perpendicular to the axis of the light source, it is not overpowered by the light source. Since the surface of the grating is formed into a tubular structure around the axis formed by the light emanating from the light source, the diffracted light is projected (in a radial pattern around) (from all sides of) that axis. The diffraction grating may be reflective or transmissive. A transmissive grating can either be mounted or molded onto the surface of a transparent or translucent support surface. The tube may be made with a reflective grating in a manner that allows some light to pass through its aggregate structure:
1. A reflective grating may be mounted or molded into the inside surface of any material, and then perforated to create a semi transparent support surface.
2. Pieces of a reflective diffraction grating may be mounted onto the inside surface of a transparent or translucent support surface so that the gaps between the pieces allow light to be transmitted through them.
3. A reflective grating may be mounted or molded into the inside surface of any material that is then cut into strips and woven into a tubular structure that allows light to pass through the open gaps of the weave.
4. A reflective grating may be mounted or molded into the surface of any material that is then assembled as a piece to an aggregate tubular structure that allows light to pass through the open gaps between the pieces.
The cross sectional shape of the tube may be circular or varied to create different lighting effects and to focus the color displays into certain directions. The walls of the tube may either be parallel, or slightly bowed or angled to each other to create other variations to the lighting effect.
Due to the linear nature of the Tube, the geometry of the spectral optics allows for great variations to the color display that are determined by the angle and distance that the tube is viewed from. This effect not only has a dynamic and engaging quality that has appeal for the decorative lighting market, but it could also be used in navigation and instrumentation, as a positioning device.
It has also been discovered that by passing water over the surface of the light tube, dynamic variations to the color effect are created. The refraction of light by the moving water surface constantly changes the angle of incidence of the diffracted light rays. Since the incidence angle effects the color of the light ray, the colors are altered by the surface pattern of the water flow.